Atypical Quantized Hall Resistances in Millimeter-Scale Epitaxial Graphene <i>p-n</i> Junctions

Epitaxial graphene (EG) on silicon carbide (SiC), which grows on hexagonal SiC at high temperatures, can be nearly defect-free on the centimeter scale and exhibits properties that make it suitable for large-scale and high-current applications. We have demonstrated the millimeter-scale fabrication of monolayer epitaxial graphene p-n junction devices using simple ultraviolet photolithography, thereby significantly reducing device processing time compared with electron beam lithography typically used for obtaining sharp junctions. This work presents the resulting experimental data obtained from these devices when introducing multiple current inputs in several different configurations. Furthermore, the LTspice circuit simulator is used to examine the various rearrangements of the electric potential in the device when injecting current at up to three independent sites. These measurements yield nonconventional, fractional multiples of the typical quantized Hall resistance at the v=2 plateau (R_H = 12.9 kΩ) that take the form: a/b *R_H. Here, a and b have been observed to take on values such 1, 2, 3, and 5 to form various coefficients of R_H. These results support the potential for drastically simplifying device processing time and may be used for many other two-dimensional materials.